Dynamo-electric machine



Feb. 28,1933.

R. N. EARLY DYNAMO ELECTRIC MACH INE' Filed Feb. 24, 1930 INVENTOR Patented Feb. 28, 1933 TES I RUPERT N. EARLY, 0F MINNEAPOLIS, MINNESOTA, ASSIGNOR TO ELECTRIC MACHIN- EEY MANUFACTURING COMPANY, BF MINNEAPOLIS, MINKESDEA.

DYNAllEQ-ELECTRIC EAGHIHE Application filed. February 24, 193%. Serial He. seems.

This invention relates to electric motors and more particularly to improvements in induction motors and synchronous motors and in starting systems for the same. This application is a continuation in part of my co-pending application Serial Numher 334,881, filed January 25, 1.929.

fit is an object of this invention to eliminate the necessity of proyicling some means external to an electric motor, such as the ordinary autotransforiner, resistor or reactor for cutting clown the voltage applied; to the primary Winding during the starting periocl in accordance with present practice. it is usually desirable and oftentimes essential to provfie some means for reducing the voltage applied to the terminals of the motor, at least until the motor has attained a considerable speed, ano. this for the reason that unless some such means is employed the current taken by the motor is excessive and may cause injury to the motor anti an undesirable surge on the line The apparatus necessary to start a motor by applying reduced voltage and subsequently applying full voltage is necessarily expensive and ordinarily the starting of'a motor in this manner involves the interrup-- tion of the primary current with the production of an objectionable line surge.

Accormiing to my invention ll proviso a motor having a primary infiing of such a nature that the current employed during the initial portion of the starting eriod may he confined within a. portion only of the primary winding although tull'voltag'e is applied to the primary. [after the motor has attainecl a speed such that application of full voltage to the entire Winding will not produce an undesirable surge on the line the remaining portion oi the primary Winning is connectedto the line to establish normal running conditions. The several motor circuits are connecterl in parallel ciuring normal operation of the machine aini it will he unilerstoocl that by employing only certain of these circuits during the initial portion of the starting periool the primary current is limited to a relatively low value. The impedance of a single Wincling circuit is greater than that of two such circuits in parallel, hence the reduction in current taken by the motor sluring the initial portion of the starting period.

My invention contemplates provision of a. motor having a polyphase primary winding, at least one phase of which inclncles two or more winiing sections. During the initial portion of the starting period some but not all of the Winding sections are connect ea to the source of polyphase current. Subse" quently, the remaining Winding sections are connecte l across the lineso that all Winning sections are in parallel relation and the motor is operating under normal running conditions. It Will he understood that current first supplied to a portion of the winoling sections aml then to all Winding sections in parallel relation, thus reciucing the value is the current initially supplie to the motor (luring the starting perioi ll may employ Winding sections for each phase which are interconnected, or I may employ Winding sections for each phase which are not interconnected. For example, 5 may employ a plurality of star-connected wining' sections, one section to: each phase, aria one or more additional sets of corresponding scctions, all sections having their neutral point interconnecterl. U11 the other hancl 1 may use a plurality of separate polyphase rrinrl ings which are not interconnected Within machine.

fill

80 in either case certain of M16 Wll'lCling sections are connecterl to the line to start the motor ancl after the rotor ias attaineol sufificient speeci the remaining Winding sections connected across the line. The several winding sections for each phase may he connecterl to seoarate switches prefers electromagnetically operated, anti l may ploy automatic or manually operable such as a push. hutton, for energizing tne ch cuit of one of the electromagnetic sr close same anti apply current to rain. of the Wincling sections. may employ automatic means for suhseqnently closing other switch to connect the remaining enaing sections across the line. seconi switch, or set or contacts, may he controlleoi by a timing device or any character hutv ll prefer to employ some means responsive to some conolition of the motor inoicetive or? the existence of sufiicient counter E. M. F. to prevent an excessive flow of current when voltage is applied to all winding sections. For example, I may em loy a relay responsive to the electric condition of the pJrimary or seconda winding and prefer ly the latter. In t e event the invention is applied to a synchronous motor the single phase secondary winding may be connected in closed circuit during the startin period and a relay which event the closing coils may be deenerized and the contacts held in closed position y the latching means. Furthermore I may provide some means, such as an overload relay responsive to an excessive load on the motor for controlling the latching means to disconnect the motor from the line whenever excessive load is placed on the machine. Also where my invention is applied to a synchronous motor I may employ means responsive to the electrical condition of the secondary winding during the starting period for controllin the application of excitation current to the eld winding.

The various objects and advantages of m invention will be more apparent upon consi ering the following detailed description which is to be taken in conjunction with the accompanying drawing, illustrating certain embodiments of m invention as applied to a synchronous mac 'ne. In the accompanying drawing I 1g. 1 is a diagrammatic representation of a synchronous motor and starting system in accordance with my invention;

Fig. 2 is a diagrammatic representation of a form of primary winding somewhat different from that illustrated in Fig. 1.

In Fig. 1, I have illustrated a synchronous motor having .a threehase star-connected primary winding A, a eld winding F and a squirrel cage or damper winding B. The leads 1, 2 and 3 represent a source of threephase alternating current, and a source of direct current is re resented by the leads 4 and 4' which may be connected to the field winging F.

Each phase of the primary winding A includes two winding sections 5 and 6, all connected to a common neutral point 7. The winding sections 5 are shown connected to contacts of a switch 8 and the winding sections 6 are connected to the contacts of a switch 9. It will'be understopd that a single switch structure may be employed instead of the two illustrated at 8 and 9 in which event the winding sections 5 are connected to one set of switch contacts and the winding sections 6 connected to another set of contacts associated with the switch. It will be understood that in the system, as illustrated in Fig. 1, the closing of switch 8 connects the winding sections 5 to the source of alternating current re resented by the leads 1, 2 and 3 and that t e closing of switch 9 serves to connect the winding sections 6 to this same source. Furthermore it appears that when both switches are closed all Winding sections are connected in parallel across the A. C. line.

In starting the motor of Fig. 1 switch 8 is first closed to supply current to the winding sections 5 and after the motor has attained a suitable speed the other switch 9 is closed to connect the winding sections 6 across the line. It will be noted that the winding sections 6 are connected to the line without in any way interrupting the connection of the winding sections 5 to the line. Accordingly, there is no interruption in the flow of current to the primar winding and no surge occurs on the line ecause of the interru tion of current as is the case when a trans er from reduced voltage to full voltage is made in the heretofore practiced manner involving the use of an autotransformer.

I have shown the switch 8 as bein operated by a closing coil 10 which may e supplied with current. from any suitable control circuit, such as that represented by the leads 11 and 11. A pilot relay 12 and a starting push button 13 are included in the control circuit and it will be understood that upon closing the push button switch the operating coil 14 of the pilot relay 12 is energized and the contacts 15 and 16 of this relay close. The closing of contacts 15 completes a seal around the push button 13 and the closing of contacts 16 serves to connect the operating coil 10 of the line switch 8 across the supply leads 11 and 11', the circuit being as follows: Lead 11, wire 17, wire 18, closing coil 10, wire 19, switch contacts 20, wire 21, switch contacts 16, wire 22 and lead 11. The closing of switch 8 serves to close auxiliary switch contact 23 associated with this switch.

As explained above, the closin of switch 8 serves to supply current to w1nding sections 5 and the rotor commences to revolve. After the motor has attainedsay 80 per cent of its normal operating speed( the particular valuedepending upon operating conditions) the switch 9 may be closed to connect the remaining winding sections 6 across the line.

The closing of switch 9 may be accomplished by means of a closing coil 24 which may be supplied with current from the control circuit represented by the leads 11 and 11. A control relay 25 may be employed for controlling the energization of the closin coil 24. This relay has an operating c011 26 and contacts 27 and 28. Means are provided for delaying the operation of the control relay and hence the closing of switch 9 until the motor is in proper condition to have its inactive primary winding sections connected across the line. I'have represented such a means in the form of a relay 29 having contacts 30 and an operating coil 31 which may be connected in circuit with the secondary winding F on the motor. The winding F is connected to c field rheostat 32 and to a field switch 33 by meansoi wires 34- and 35. lhe field switch 33 is open during the starting period and auxiliary contacts 36 associeted with the field syntcii serve to conmeet the field winding in closed circuit during the sterting period through resistance elements 3? and 38. A. resctence 3% is also connected in the field circuit and on operating coil ll} of s frequency relay is, connected across the recctsnc'e 39 by means of wires 42, 43. This frequency relay has normally closed contests 44: and normally open contacts 45. The 0 erating coil 31 of the relay 29 is connected across the resistance element 38 through contacts 45 of the frequency relay by means oi wires i6, i7 and the wire 42.

When voltage is first applied to the motor an induced current of slip ireqnency is indnced. in the field circuit and a relatively large portion of this current flows through the coil 46 of the frequency relay 4 due to the fact that this coil is connected across the resctance 39 which is in series with the field winding. The frequency rein-y immediately operates to open the contacts id and close the contscts 15, The closing or contacts 4:5 inserts reloy coil 31 in parallel with resistor 38. This resistor 38 has relatively high rcsistcnce and, accordingly, a large part of till the induced field current flows through relay coil 31..iWhen the motor speed reaches a value such that it is appropriate to connect the winding" sections 6 or the primary winding across the line the frequency oi the induced field current has reached such s, low value that the relay 22 closes its contacts 36, A damper ring l8 on the core of this relay preyents closing" of the contacts 30 until the frequency of the current flowing through the relay coil 31 is reduced to a predetermined value corresponding with s motor speed such that the winding sections 6 may be connected to the line without producing undesirable lino surge. I

The operation of relay 29 serves to supply current to the operating coil 25 of the control relay 25, the circuit including the wires l9 and 5t), connecting switch contacts 18 or the pilot relay 12 and contacts 36 of the relay 29, and the wires 51 and 52-connecting the con trol relay coil 26 with the relay 29 and the operating coil 14 of the pilot relay 12. When the control rela operates, its contacts 27 and 28 are closed. he closing of contacts 28 completes a seal around the contacts 30 of the relay 29 and the closing of contacts '27 serves to connect the operating coil 24 of the line switch 29 to the control circuit. The circuit for operating coil 24 isas follows: lead 11', wire 17, wire 18, wire 53, operating coil 24, wire 5-1, switch contacts 27 of the control relay 25, wire 55, wire 19, auxiliary contacts 20 of the field switch 33, wire 21, contacts 16 of the pilot relay 12, wire 22 and lead 11. It will he noted that energy is supplied to the operating coil of t e line switch 9 through the closed contacts 16 of the pilot relay 12, and accordingly, the switch 9 cannot be closed until the pilot relay is energized and current supplied to the operstingcoil of line switch 8. The closing of line switch 9 causes auxiliary contacts 56 associated therewith to close and it will be noted that the e contacts are connected in series with the auxiliary contacts 23 of the line switch 8 by means of the wire 57. Thus when both auxiliary contacts 23 and 56 are-closed, current is supplied to latching coils 58 and 59, the circuit being from control wire 18 through latching coils 58 and 59 and wire 60 to contacts 56, wire 57, contacts 23 and wire 61 to the'control circuit wire 49.

When the motor reaches a speed near synchronous speed the coil 40 of the frequency relay il becomes decnergized whereupon contacts 44 close and contacts l5 open. The closing of contacts re serves to supply current from the control circuit or" on operating coil 62 associated with the field switch 33. The circuit for this operating coil 62 is as follows: Lead 11, wire 1?, wire 63, closing coil 52, wire 64:, switch contacts 44 of the frequency relny 41, wire 65, auxiliary switch contacts 56,

wire 57, auxiliary switch contacts 23, wire 51,

Wire re, contacts 16 of the pilot relay 12, wire 22 end lead 11.

lhe closing of the field switch 33 serves supply excitation to the field winding from the source of direct currents represented by the lends 43 end if. The closing of this field switch also serves to open the suxilisry field contracts 2% and 36. The opening of contacts 36, disconnect-s the discharge resistance 3? from the field winding F, and the opening of the snXilie-ry contacts 26 interrupts the flow of current from the control lends 11 and 11 to the closing coils 9 and or of the line switches 8 end 5% and it will he understood that theres-iter these switches are held in closed po sition by the latching coiis 58 end 59.

As pointed out shove latching coils 5 end 59 are energized through the contacts 1 of the pilot reloy12. The operating coil 1 of this relay derives its current from the control leads through contacts (58 of an overload relay 6? and the contacts of spnsh hutton 68. By pressing the button '68 the pilot reley is deenergized and in turn the latching Lit) coils 58 and 59 are deenergized to open the lineswitches 8 and 9. Also the operating coil 62 of the field switch is deenergized and this switch opens to disconnect the field winding from the source of direct current. In like manner the motor is disconnected from the line and from the source of direct current whenever the overload relay 67 operates to open its contacts 66. The overload relay 67 is connected to current transformers 69 in the usual manner and an ammeter 70 may also be connected to the current transformers 69 to indicate the value of the line current.

In Fig. 2 I have illustrated a primary motor winding similar to that shown in Fig. 1 except that the neutral point of winding sections 5 is not connected to the neutral point of winding sections 6. Accordingly, two entirely separate circuits are provided on the primary member. It will be understood that a motor having a primary winding, such as that illustrated in Fig. 2, may be started in exactly the same manner as that described in connection with Fig. 1. The winding sections 5 of the winding of Fig. 2 may be connected to switch contacts and winding sections 6 to separate switch contacts whereby the two sets of winding sections may be independent- 1 connected to the line in succession as above escribed.

The invention, as illustrated in the form illustrated in the accompanying drawing, in-

cludes a synchronous motor having two winding sections for each phase of the primary winding, means for lndependently connect ing these winding sections to the line in succession as determined by the operation of a delaying device in the form of a relay responsive to the induced field current and the primary switch contacts which are effectively interlocked to prevent simultaneous closing of all contacts and to insure closing of the contacts in proper sequence. Furthermore the excitation current is automatically sup plied to the field winding in accordance with the condition of the field winding.

It is to be understood that my invention is not limited to the s cific embodiments illustrated and describe but includes such modifications thereof as fall within the scope of the a pended claims. For example, while I have il ustrated primary windings each phase of which consists of two winding sections it is to be understood that each phase may include more than two winding sections and the expression com rising two winding sections employed in t e appended claims is intended to define a windm having two or more winding sections per p ase.

I claim:

1. The combination of an electric motor having a polyphase primary winding a plurality of phases of which each comprise two winding sections, a source of alternating current, separate switches for connecting the sections of each of said pluralit of phases to said source, means for c osing said switches, and means for delaying the closing of one ofsaid switches until after the other switch has been closed, whereby current is first supplied to one of said sections and then to both sections in parallel relation.

2. The combination of an electric motor having a polyphase primary winding a plurality of phases of which each comprise two interconnected winding sections, a source of alternating current, separate switches for connecting the sections of each of said plurality of phases to saidsource, means for closing said switches, and'means for delaying the closing of one of said switches until after the other switch has, been closed, whereby current is first supplied to one of said sections and then to both sections in parallel relation.

3. The combination of an electric motor having a polyphase primary winding a plurality of phases of which each comprise two winding sections, a source of alternating current, separate switches for connecting the sections of each of said plurality of phases to said source, means for closing one of said switches, electromagnetic means for closing the second switch,-means for energizing said electroma netic means, and means for delaying the cfiising of said second switch until after the other switch has been closed, where by current is first supplied to one of said sections and then to both sections in parallel relation.

4. The combination of an electric motor having a polyphase primary winding a plurality of phases of which each .comprise two winding sections, a source of alternating current, separate switches for connecting the sections of each of said plurality of phases to said source, means for closing one of said switches, electromagnetic means for closing the second switch, means for energizing said electromagnetic means, and means for delaying the energization of said electromagnetic means until after the first switch has been closed, whereby current is first supplied to one of said sections and then to both sections in parallel relation.

5. The combination of an electric motor having a polyphase primary winding a plurality of phases of which each comprise. two winding sections, a source of alternating current, separate switches for connecting the sections of each of said plurality of phases to said source, means for closing one of said switches, electromagnetic means for closing the second switch, means for energizing said electromagnetic means, and electromagnetic means for delaying the energization of said electromagnetic means until after the first switch has been closed, said delaying means being deenergized until said first switch has been closed.

6. The combination of an electric motor having a polyphase primary winding :1 plurali of phases of which each comprise two win ing sections, a source of alternating current, separate switches for connecting the sections of each of said plurality of phases to said source, electromagnetic means for closing said switches, and means for delaying the closing oi one'oi said switches until after the other switch has been closed, said delayingrneans losing responsive to the electrical condition oi the motor '8. The combination of an electric motor having a secondary winding and a polyphase primary winding a plurality oi phases of which each comprise two winding sections, a source of alternating current, separate switches for connecting the sections of each ri plurality ofphases to said source, ill? controllable means for closing one I oi said switches and means responsive to the ion of one of the motor w1nd.-'

electrical con ings closing the other switch,

9., The ccnihination of an electric motor having a secondary winding and a polyphase pi "ry a plurality of phases of which'each comprise two winding sections, a source alternating current, separate switches for connecting the sections of each plurality of phases to said source, controllable means for closing one id switches, and means responsive to the rical condition of the secondary winding for closing the other switch.

it The combination of an electric motor having a secondary winding and a polyphase primary winding plurality, of phases of which each comprise scarce alternating current, separate switches tor connecting the sections of each l'urality of phases to said source, closin coils for said switches, manually oppg m erahle ineans for energizing one of said closing coils, and means responsive to current in the'secondary winding of said motor for energizing the other closing coil.

. ii. The combination of an electric motor having a secondary vwinding and a polyphase primary at least one phase of which comprises two winding sections, a source or alternating current, separate switches for said sections to said source, clos- 7. The combination of anelectric motor two winding, sections, I a,

ing coils for said switches, manually operable means for energizing one of said closing coils, means responsive to current in the secondary winding of said motor for energizing the other closing coil means for latching said switches in closed position, and means responsive to current in the secondary winding for deenergizing said closing coils.

12. The combination of an electric motor having a secondary winding and a polyphase primary winding at leastone phase of which comprises two winding sections, a source of alternating current, separate. switches for connecting said sections to said source, clos ing coils for said switches, manually operable means for energizing one of said closing coils, means responsive to current in the secondary winding of said motor for energizing the other closin coil, ineans for latching said switches in c osed position, means responsive to current in the secondary winding for de energizing said closing coils, and means responsive to an overload on the motor for releasing said latching means.

The combination of an electric motor having a secondary winding and a polyphase primary winding at least one phase of which comprises two winding sections, a scarce oi alternating current, separate switches for connecting said sections to said source, clos- 111 coils for said switches, manually oper able means for energizing one of said closing 0011s, moans responsiveto current in the ondary winding of said motor for eneraiain the other closing coil, means for latchin sail switches in closed position, and rneaiis re" source of direct current.

' The combination of an electric motor having a polyphase primary winding at le t onaphase of which comprises windini: sections, a source of alternating current, sen arate sets of switch contacts for connectin the sections oi each of said plurality phases to said source, means for closing said contacts, and for delaying the closing of one set of said contacts until after other set has been closed, whereby current is first supplied to one of said sections and then to both sections in parallel relation.

15. The combination of an electric having a secondary winding carrying an induced current during the starting period apolyphase primary winding a plurality oi phases of which each comprise two winding sections, a source of alternating current, separate switches for connecting the sections oieach of said plurality of phases to said source, means for closing said-switches, and means for delaying the closing of one of said switches until after the other switch has been closed, whereby current is first supplied dam o alternating current, separate switches for connecting the sections of each of said plurality of closing sard switches, means for delaying the closing of one of said switches until after the other switch has been closed, whereby current is first supplied to one of said sections and then to both sections in parallel relation, a source of excitation current and means for connecting said source of excitation current to said field winding when the motor has nearly reached synchronous speed.

17. The combination of a s nchronous motor having a single phase eld winding, 3. polyphase primary winding, a plurality of phases of which each comprise two winding sections, means for connecting said field winding in closed circuit during the starting period, a source of alternating current, separate switches for connecting the sections of each of said lurality of phases to said source, means for c osin said switches, means for delaying the closing of one of said switches until after the other switch has been closed whereby current is first supplied to one oi said sections and then to both sections in parallel relation, a source of excitation current and means for connectin said source of excitation current to said eld winding when the motor has nearly reached synchronous speed. r

18. The combination of a synchronous rate switch contacts for connecting said pri- 55 a source of current, a field an mary connections to said source, means for closlng said switch contacts in sequence, a source of direct current, and means re 'sive to current induced in said field win for interrupting the closed circuit connection of said field winding and for connecting said field winding to said source.of direct current.

19. The combination of a synchronous motor having a single phase field winding, a polyphase primary winding at least one phase of which comprises two winding sections, a source of alternating current, separate switch contacts for connecting said sections to said source, electromagnetic means for closing said sets of contacts in sequence,

phases to said source, means for connect the field winding to said source of.

direct current, and means for preventing the operation of said field switch until all of said switch contacts have been closed.

20. In combination, a supply circuit, a squirrel-cage polyphase motor having a plurality of electrically independent similar phase circuits on its stator, a predetermined number of said circuits being connected in star and the remaining circuits being arranged for connection in open circuit star and in parallel relation with said other circuits, a switch for connecting said predetermined circuits to said supplycircuit while the remaining circuits are in open circuit star, and means operative in accordance with a predetermined sub-synchronous speed of said squirrel cage for closing the open circuit in said remaining circuits.

21. In combination, an alternating current supply circuit, a direct current source of supply, polyphase synchronous motor having a primary member provided with a plurality of electrically inde ndent similar phase circuits and a secon ary member including a squirrel-cage winding and a direct current exciting winding, a switch for connecting one of said primary circuits to said supply circuit while another of said primary circuits is idle, and switching means operative in accordance with the speed of said secondary member for connecting said other circuit in parallel relation with said one circuit and for connecting said exciting winding to said direct current source.

22. In combination, an alternating current supply circuit, a direct current source of supply, a polyphase synchronous motor having a primary member provided with a plurality of electrically independent similar phase circuits and a secondary member including a squirreLcage and a direct current exciting winding, a predetermined number of said primary circuits being connected in star and the remaining primary circuits being arranged in o n circuit star and for connection with said other stator circuits a switch for connecting said redetermined primary circuits to said supp y circuit while the remaining primary circuits are idle, and

switching means operative in accordance with the speed of said second member for clomng the open circuit in said remaining primary circu ts and for connecting said exciting windin to said direct current source.

23. In com ination, a supply circuit, a squirrel-ca polyphase motor having a primary mem r provided with a plurality of electrically independent circuits in each of its stator phases and a secondary member, a predetermined number of said stator circnits'be-V ing connected in star and the other stator cir- 5 cuts having one set of terminals connected to terminals of said predetermined stator cirsuits and arranged for connection in star with neutral end connections in open circuit, switching means for connecting said prew determined stator circuits to be energized from said supply circuit and switching means operative in accordance with a prede' terinined speed of said secondary member for connecting all of said stator circuits in perni- 35 iel relation in e pinreiity of independent neutrai star-connected gronps.

24; The combination of a synchronous motorhcving a singie phase field Winding a poiyphase primary Winding, a plurality of 20 phases of which each comprise two Winding sections a source of alternating current, sepcrate switches for connectingthe sections of each of said plurality of phases to said source, means for closing said switches, means for deieying the closing of one of said switches until after the other switch has been ciosed Wnerehy current is first supplied to one of said sections then to both sections in pareiiei relation, as source of excitation current and means connecting said source of excitation current to said fieid Winding when the motor has nee-fly synchronous spec in comhinction, e supply circuit,

" sqnirrei-cege motor having e primery member ided pinreiity electrically circuit in each of its stator phases and a secondary i'neniiier e determined number oi stetcr circuits 70eing conn cted in star the other stator circnits connected open star, switching means coiinecti g predetermined i: cneigized from said supply circ it and switching means operative in accordance with. a predetermined speed of said secondary member for connecting sit of said statcr circuits in pereiiei relation in e pinreiity of independent nentei stsr-connected groups,

in testimony wneiec: my signetnre,

Rib? N, AERLY.

CERTIFICATE OF CORRECTION.

Patent No. 1,899,858. February 28, 1933.

RUPERT N. EARLY.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, line 56, for "winging" read "winding"; page 5, lines 107 and 108, claim 14, strike out the words "at least one phase of which comprises" and insert instead "a plurality of phases of which each comprise"; page 7, line 5, claim 23, for "cute" read "cuits", and line 37, claim 25, for "circuit" read "circuits"; and that the said I LettersPatent should he read with these corrections therein that the same may conform to the record of the case in the Patent Office Signed and sealed this llth day of April, D. 1933.

M. 'J. Moore. (Seal) Acting Commissioner of Patents. 

